Submarine signaling.



J. B. MILL'ET.

SUBMARINE SIGNALING.

APPLICATION FILED JUNE 23, 1909.

Patented Nov. 22,1910.

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JOSIAH B. MILLE'r, or BOSTON, mssacnusnr'rs, Assrenon TO MInLE'r SIGNALcom- PANY, or nosron, mssacnusnrrs, A CORPGRATION or- MAINE.

sun SIGNALING.

sileeific ion of Letters Ilat'ent- I Patented Nov. 22, 1910.,

Application filed June 23, 1909. Serial No. 503,801;

To all whom it may concern;

Be itknown that I, JOSIAH B. Mums-'1', a citizen of the United States,residing at Boston, in the county of Suifolk and State ofh/Iassachusetts, have invented an Improvement in Submarine Signaling, of.which the following description, in connection with the accompanyingdrawings, is asary to turn the latter partly around beforespecification, like letters on the drawings representing like parts.

lily invention relates to submarine signaling, being more particularlyintended to provide a simple form of detecting apparatus and a simpleand efiicient method of determining the direction of a source ofsubmarine sound.

Heretofore, for the purpose of ascertaining the direction of a source ofsubmarine sound on a'vessel or the like, it has been customary to equipthe vessel with two sets of detecting. devices arranged, one at a pointon one side of the vessels hull, and the other at a point on theopposite side of the hull.

Through a comparison of the intensity of the sounds received by thesedifiierent sets of devices an estimation is made of the direction fromwhichihe sounds come.

As the ships skin or plating gradually curves from stern to how, itshull constitutes in effecta curved receiving surface by which ing andthe direction of sound propagation is less than the critical angle thesound is largely reflected and is without substantial effect upon asounddetector acoustically applied to the ships plating at such point.

vWhere the ships hull, therefore, has been utilized as a receiver ofsubmarine sound, it-n has been usual heretofore, in order to obtainexact direction, to swing the vessel or deflect -it from its course moreor less until the sounds heard on each sideare alike in intensity,thereby locating the source of sound -"as directly ahead. Or the vesselmay. be

"swnng until the sound as received by the detector on one side is at itsgreatest intensityshowing that the source is at right angles to thevessels side at that point. Since it is often impossible, and frequentlyinconvenient, to swing the vessel from its course, it has often becomediflicult to obtain accurection on a floating structure.

ample, if the source of sound were over the' stern quarter'of the vesselit would be necesthe sound could be heard at all. Moreover,

even where the source of sound is so located with respect to one or theother of the two sound detectors as to enable the sound to act upon onewith greater intensity than upon the other, the employment of two ormore detectors, particularly where electro-microphonic detectors havebeen employed, is more or less unsatisfactory, because the detectors, ifequally sensitive at one time, are apt to undergo more or less change,and as time passes, become unequally sensitive so' as to rendercomparative tests for sound intensity Y unreliable. This is;particularly true of granular carbon microphones Where the carbon notonly tends to pack in the course of time, but also todeteriorate or topack in a few minutes through continued heating by the electric current.With the'use of a plurality of granular detectors, therefore, Whatappears to the listener to be the direction of greater intensity ofsound may, in fact, be the directionof lesser intensity owing to theunequal sensitiveness of the two detectors.

In carrying out my invention I arrange for the acoustic ap lication of asound detecting device, and preferably the same sound detecting device,to difierent points on the interior of the ships skin or plating. Bythis method the same detector can be transferred from one point toanother and the entire ships plating followed around if necessary, untilthe point is found at which the sound is received with the greatest in-'with greatest intensity, the precise direction can readily beascertained from a comparison of the intensity of the sound at differentpoints on the interior of the ships hull.

. ships hull or to The direction of the source of sound, therefore, canbe ascertained readily, in a simple and convenient way, without alteringthe vessels course.

My invention, furthermore, in certain of its aspects relates'to animproved form of apparatus intended more particularly, though notexclusively, for use as a portable apparatus and one which may beacoustically applied at different points on the parts in good acousticcontact therewith. I My invention has other objects both related andunrelated to the foregoing, but these as well as the purposes alreadyspecified will be best understood by reference to the followingdescription when taken in connection with the accompanyingillustrationof one specific embodiment thereof, while its scope will bemore particularly pointed out in the appended clalms.

In the drawings: Figure 1 shows diagrammatically a system of submarinesignaling in conjunction with which one form of my invention may beutilized. Fig. 2

- is a central, lon itudinal section taken through the 'porta ledetecting apparatus shown in Fig. 1; Fig. 3 is a section-in plan on theline 33 in Flg. 2; Fig. 4. is an illustrative diagram; Fig. 5,is asection showing a modified form of detector; and Fig. 6 is a detailshowing another modification.

While my lnvention as to certain of its aspects is susceptible ofapplication to Widely different uses, for the sake of illustration andwithout restricting its employment to any one particular purpose, I haveherein shown'its application to a system of submarine signaling whereinthe submarine sounds are detected byacoustical contact with difierentparts of the ships hull.

Referring to Fig. 1 I have there represented a sending station forsending submarine signals to a distant receiving station, the latterbeing represented as a vessel or other partlysubmerged structure, havingits hull provided with the skin or plating 1. The sending apparatusmaybe of anyusual or suitable type, but herein the same is conventionallyrepresented by a wellknown form of submarine sound producer comprisingthe submerged bell 2 sustained bythefioat 3 and adapted to be moved orstruck for the creation of sound vibrations within the Waterthrough'means well understood by those skilled in the art.

electro-microphonic agency for electrically for.

The

the listener.

able or non-portable, preferably I employ a portable apparatus havingthe handle 4, by means of which the detector may be conveniently appliedto the interior of the ships skin or a body acoustically connectedthereto.

As shown in Fig. 2, the handle is attached to the hollow stem 5,, to theend of which is-secured, as by threaded engagement therewith, themicrophone support 6, herein in the'form of an open elliptical ring-likeframe;

The microphone may be of any desired construction Ortype, my inventionbroadly considered having no particular reference to the detailedconstruction of the microphone itself. In the illustrated form, however,it is shown as of the variable resistance type, in the form of a commonmicrophone but-ton, rigidly and mechanically attached by the threadedstem 7 to the support '6. The stem supports the carbon electrode .8,

which latter is secured to the mica disk or diaphragm 9. The mica diskis attached to For the microphone there are provided connections to anappropriate listening device. These may be of any suitable character,but herein the electrode 8, being attached to the support 6, is therebyelectrically connected to the stem 5 and handle 4. The electrode 11 isconnected through the casing 10 to a conductor 14, whichlatter isembedded in the tube 15 of insulating materialfitting tightly within theconnecting stem 5. The conductor -14 passes through the stem to thehandle 4 where it is appropriately connected to the batterycells 16 and17, which are conveniently mounted in the handle and within theinsulated lining 18 there- The batteries are serially connected witheach other,- and, through the-spring contact 19, also with the bindingpost 20, a binding post 21 beingemployed for contact with the casing andthe electrode 8. The two binding posts in turn are connected to asuitable listening device, herein in the form of a head telephone 22,having two receivers connected by a resilient band which holds thereceivers in position against the ear of.

- .iwepaa can hold the detector in his hand and carry thesame from placeto place, manually applying the detector to such points of the ,shipshull as he Wishes to test, the entire apparatus, detector, batteries,receivers and connections being thus readily portable to.

different parts of the vessel and easily applicable when and wheredesired;

. To secure a good acoustical connection or contact between themicrophone and the.

ships hull, the microphone support 6 may be provided with a contactmember 23 hav- 15.

ing'a small contact. area, as for example, a point or sharp edge, andherein consisting of a pointed metallic projection secured to themicrophone support 6 and preferably substantially in line with thehandle and stem so that when pressed against the ships skin,-

or a body having acoustical connection therewith, a good contact may besecured with such body and a good sound conducting connection maintainedbetween the said body and the microphone through the point 23 and themetallic support 6. In.acous tically applying the detector to the shipshull it may be directly applied to the inte-' rior of the ships skinitself or to some good sound conducting body in acoustical connectionwith the ships skin. Through the manual applicationofthe contact pointto the ships skin or other connected part an excellent acousticalconnection is secured to the microphone, rendering the latter delitheships hull."

The microphone being otherwise openly exposed to the influence of theships noises propagated through the air within the ship, means arepreferably providedfor protecting the microphone against such extraneoussounds so as to exclude from influencing the microphone 'substa-ntially,,all sounds except those propagated through the ships hull.-

' For the purpose of excluding air-propagated sounds there is shownattached to the stem 5 an open-endedprotectiiig casing-24 which may be'made of metal, but is preferably of such material and thickness as tobe capable of excluding such sounds as are propagated through the airwithin the ship.

Such, casing has threaded engagement with the end of the stem 5, thehead of the casing being split and provided withthe clamping screws 25so that it may be adjustably positioned on the stem relatively to thecon-. tact member 23. To the edge of the open end of the casingthere'ispreferably secured a yieldable sound-excluding wall, such as therubber gasket or other packing 26 of suitable size and thickness, whichis adapted to rest against any solid body to which the detector may beapplied. This not only from the ships skin to the microphone exceptthrough the contact member.

In addition to the ships noises or extraneous sounds propagated throughthe air, there ordinarily arise avariety of confusing noises, voriginating partly without but chiefly within the vessel, which arepropagated through the material of the'ships plating. Means aretherefore preferably employed for also excluding such noises from themicrophone, leaving the latter substantially responsive only to the morepurely musical notes of the signal bell. In this connection I havediscovered that, by interposing aproperly proportioned solid body ofsuitably selected material in the acoustical conducting path between themicrophone and the vibrating solid or liquid mass to which it isapplied, sounds that are unmusical and sounds that are of slightintensity, or of low pitch, or such as have vibrations of short durationas compared with the sustained periodic vibrations of a. more purelymusical tone, may be largely intercepted and excluded from access to themicrophone while still leaving the more intense sounds of sustainedduration, and particularly the musical sounds of regular periodicity andrelatively high pitch, only slightly impaired in strength. Thisfact maybe utilized to provide a selective device in submarine signaling byinterposing such a body between the microphone and the ships skin, suchbody serving to eliminate in a large measure the so-called ships noiseswhile permitting the musical note of the signal bell to pass through tothe microphone.

' I have found that many substances having low elasticity in relation totheir density, and which 'are generally considered to be poor orrelatively poor conductors of sound,

such as rubber, leather, soft paper, and the like, have this property ofselective conductivity of sound so that, by interposing a suitablyproportioned body of rubber, for

example, in the conductive path of the microphone, the result abovedescribed can be attained.

In Fig. 2 I have shown a body 31 interposed between the contact member23 and the ships plating, such body herein consisting of a plate or diskof rubber, although, as stated above, paper, leather, and a greatvariety of other materials may be employed for this purpose. Thethickness and the material comprising 'the interposed body may beselected according to volume and intensity of the ships noises to bedealt with. In Fig. 2 I have shown the rubber disk 31 as fixedly orpermanently applied to the ships skin. If desired, however, it may beattached to the contact member and be transported therewith from placetoplace. Such construction is shown in Fig. 6 where the contact member 32has cemented or otherwise secured to its end the disk 33 of rubber orother material of low conductivity. The disk may, if desired, be of muchgreater thickness than is shown. The contact member'32, being removablefrom the microphone support, the latter may be provided with a number ofsuch contact members equipped with similar attachments of difi'erentthickness or material from which selec- 1 tion may be made according tothe amount and character of the ships noises which it is desired toexclude from the microphone.

In Fig. 5 I have shown a modified form stantially the same constructionas that shown in Fig. 2 is secured to a support con- 'sisting of a solidmetallic casing 29 completely surrounding and inclosing-the microphone.This gives a direct metallic sound conducting connection between the 7contact member and the microphone, so that the vibrations of thesubmarine bell are transmitted by contact-from the ships plating. It isnot necessary that the entire casing 29 should be of metal, but it ispreferably of sufiicient thickness and suitable material to exclude thegaseously. propa: gated-sounds, and it is preferably provided .with themetallic or other solid conducting While the casing 29 attached to thestem 5 may be used alone to protect and carry the microphone, ifdesired, a protecting casing 30 similar to the casing 24 may beaddiindicated' in dotted lines. the sound-obstructing material asdescribed, suitably proportioned to exclude the local sounds in anygiven case (ships difi'ering in this regard), "and combined with asensitively constructed and' positioned micro-.

phone, the bell sound may be made to distinctly predominate forsignaling purposes, thus securing in a large measure the function of theusual tank filled with water, in which in ordinary practice, themicrophone is suspended;

Heretofore, where a granular microphone has been employed, it has beencustomary, in order to secure the greatest sensitiveness, to arrange theelectrodes parallel with the sides ofthe' ship, 2'. e. lengthwise theship. This, however, is transverse to the plane-of the maximum shipsmotionsothat theeffect of the rolling of the ship is to tip the electrodesback and forth. The granular mate-i rial thereby undergoes alimited movement, but such' movement is by way of partial Withdrawalalternately from each electrode,

thereby changing the contact relations beof detector wherein amicrophone of sub path referred to of relatively great mass.'

tionally employed, such construction being By the use of tween themicrophonic material .,a'-nd the granular material.

I preferably apply the microphone to the" ships side with'its electrodeslying in planes v substantially transverse to the vessel, so that thelateral or transverse rolling movement, which is the maximum shipsmovement, can be utilized to agitate the carbon granules withoutsubstantially changing the contact relations between the granules andthe electrodes. Thus, itwill be seen thatwith the detector applied, asshown in Fig. 2, the rolling of the ship will act to shift the entiremass of granular microphonic material between the two electrodes,thereby tending to maintain it in the permanently loose and freecondition in which it was originally introduced into the apparatus.Becausethe electrodes lie in the plane of the ships rolling movement,however, this movement of the granular material does not affect the areaof contact which it maintains with each of the two electrodes.

In order that the microphone may beheld with its electrodes lyingtransversely the ves-' sel so that transverse rolling of the vessel maybe utilized to move the carbon granules and prevent packing not only isthe microphone so mounted as to facilitate this, but a ga ge orreference mark or character 37 r (Fig- 2) may be employed upon thehandle to indicate to the operatorwhen the microphone within the casingis in the desired position.

Heretofore it'has been attempted to determine direction by fixeddetecting instruments located ordinarily at opposite sides of thevessel, as, for example, at the points 27 and 28 (see Fig. 4). As abovestated,

however, not only does the comparison by two different instruments ofthe sounds received atopposite sides of the vessel introduce more orless unreliability, but, with the vessel holding. to a fixed course,sounds propagated by a source which is located without the criticalangle (roughly indicated by m and y in Fig. 4) are the only ones whichdifferentially affect .the two parts 27 and 28 of the ships skin, andthe exact determination of direction as to those sounds cannot bereached by the method. hitherto employed without turning the vessel.

In making use of the above described portable apparatus the operator cancarry it from one point to another, quickly ascertaining the quarterfrom which the sound comes. Having ascertained the general direction,the location of its source can be more precisely determined by testingadjacent portions of the-vessels skin. ..It will be seen that, byfollowing around the ships hull, the entire 360 of the horizontal planemay be investigated as to sound direction, irre-' spective of the shipscourse, and the intensities of the sounds received at all desired pointsmay be compared by using the same nodes so that, even at that part ofthe ships skin where the sound is most intense, there v are frequentlylocalpoints but a short distance apart of relatively greater and lesserintensity. The extent of this local variation will differ with thecharacter of the construction of the vessels hull, the nature of thesound and other conditions, but where a permanently fixed detector isemployed it may result in detecting the sound at a point in the shipsskin where it is relatively weak as compared with a point perhaps in thesame plate of the hull and but a short distance away. By the use of aportable detector, however, as above described, not only may that partof the vessels hull be located whereat thejsound is received with thegreatest intensity, but the particular point in that part of the vesselsskin which is subjected to the most intense vibrations can beascertained and utilized and no mistake can follow from the applicationof the detector to a nodal point in the ships skin.

lVhile I have herein shown and described one specific form of myinvention and one particular method of determining the direction ofsound, itis to be understood that the invention is not limited to theparticular details disclosed, nor to the specific construction or formor relative. arrangement of parts described, but that extensivedeviations may be made from the disclosure without departing. from thepirit of the invention.

Having thus described my invention-,what I claim is:

1. The method of determining on board a vessel or the like the directionof a source of submarine sound, which consists in acoustically applyinga microphonic sound detector to one part of the ships hull, transferringand acoustically applying the same detector to another part of the-shipshull, and comparing the relative intensities of the sounds produced.

2. The me hod of determining on board a vessel or the like the directionof a source of submarine sound, which consists in elec-.tro-microphonica'lly converting a submarine sound received at one partof the ships hull into audible sound, similarly converting through thesame agency sound received from the same source at anotherpart of: theships hull and comparing the intensities of the two audible sounds.

3. The method of determining on board a vessel or the like the directionof a source of submarine sound, Which consists in ascertaining thatpoint in the ships hull at which the sound is received with the greatestintensity, and estimating from the location'of said point and thecurvature or shape of the vessels hull thereatthe direction of the saidsound source.

4. The method of detern'iining on board a vessel or the like thedirection of a source of submarine sound, which consists in transferring from one part ofthe vessel to another an electro-microphonicdetection agency, applying the same agency by acoustical contact todifferent points in the ves= sels hull, and comparing the relativeintensities of the sounds received at ditt'erent parts of the vesselshull.

The method of microphonically detecting submarine signals on shipboardwhich consists in placing the. microphone in acoustic connection withthe side of the ship and so maintaining it as to utilize the transverserolling of the vessel to agitate the granules without substant'ii'illychanging the contact relations between the granules and the electrodes.

In testimony whereof, I have signed my name to this specification, inthe presence of two subscribing witnesses.

JOSIAH B. MILLIGT. WVitnesses:

EVERETT S. EMERY, THOMAS B. BOOTH.

